1. Field of the Invention
The present invention relates to couplings for connecting one shaft with the other shaft and more particularly, to a coupling adapted to connect roller shafts in a drafting means for use in a high-speed spinning machine.
2. Prior Art
A spinning machine for producing spun yarn from a supply of sliver comprises a drafting section drafting the sliver, a twisting section giving twists thereto, and a take-up section. In a spinning factory, a plurality of spinning machines constructed as above are disposed in parallel relation to each other.
In said plurality of spinning machines arranged in parallel, only one driving shaft is employed for the respective drafting rollers and rollers adapted to take-up the spun yarn from the twisting section. This is due to the fact that it is not economical to provide a driving source for each disposed machine. For example, in a three-roll drafting means having two pairs of back rollers, middle rollers and front rollers, only one driving shaft is provided at the front rollers for each disposed machine and the respective rollers are driven for rotation by only one driving source.
It will be noted that the use of a long shaft may result in difficulty in its transportation, arrangement, or removal and rearrangement when floating fibers are attached to part of said shaft. It is for these reasons that generally, a plurality of short shafts are connected to form a long shaft in each disposed machine.
Heretofore, there has been proposed a screwed fitting method as one of means for connecting the shafts as shown in FIG. 7. That is, an end (a) of one shaft in the form of an internal thread is threaded onto an end (b) of the other shaft in the form of an external thread so as to connect the shaft with the other shaft. However, accuracy in thread cutting of said external and internal threads is limited and thus, these threads may not completely be threaded together, no matter how much its accuracy is improved. Accordingly, the center of rotation of the shafts is likely to shift or move at a threaded portion, or a portion where the shafts are connected and the speed of rotation of the rollers fitted on the shafts may vary upon occurrence of such movement. Variation in said speed of rotation causes irregularity of drafting and uneveness of spun yarn in thickness. That is to say, as the peripheral speed of the rollers is high, the rate of drafting becomes relatively high and thin span yarn results due to excess drafting. On the contrary, as said speed of rotation thereof is low, the rate of drafting becomes relatively low. Thus, thick span yarn results.
Further, a metal joint may be employed to hold ends of two shafts. Upon use of said metal joint, deformation of the shafts due to its movement or the like barely occurs. On the other hand, connection per se is difficult to be effected. In other words, when a plurality of arranged spinning machines are installed in a factory, slight error of arrangement may occur. The joint is required to allow said error to a certain extent. However, the metal joint provides no such allowance. Also, even if the connection is effected, the position of the spinning machine may slightly shift due to vibrations of the installation floor. In such a case, disorder of the drafting means may results. Therefore, the joint needs to have cushioning effect.
On the other hand, a resilient joint may be used to hold the ends of two shafts. The above-mentioned cushioning effect is satisfied by the resilient joint. However, rotational torque may partly be absorbed thereby and as a result, the speed of rotation of the shafts becomes uneven. Thus, irregularity of drafting and uneveness of spun yarn in thickness may result as well as the above-mentioned screwed thread means.